Plumbate

In chemistry, a plumbate often refers to compounds that can be viewed as derivatives of the hypothetical PbO2−3 anion. The term also refers to any anion of lead or any salt thereof. So the term is vague and somewhat archaic.

Examples

Halides

Salts of ([PbI₃]⁻)_n, [Pb₆I₁₆]⁴⁻, [Pb₁₈I₄₄]⁸⁻, etc. are labeled as iodoplumbates. Lead perovskite semiconductors are often described as plumbates.

Lead oxyanions

Plumbates are formed by the reaction of lead(IV) oxide, PbO₂, with alkali. Plumbate salts contain either the hydrated hexahydroxoplumbate(IV) or plumbate anion [Pb(OH)₆]²⁻, or the anhydrous anions PbO2−3 (metaplumbate) or PbO4−4 (orthoplumbate). For example, dissolving PbO₂ in a hot, concentrated aqueous solution of potassium hydroxide forms the potassium hexahydroxoplumbate(IV) salt K₂[Pb(OH)₆]. The anhydrous salts may be synthesized by heating metal oxides or hydroxides with PbO₂.

The most widely discussed plumbates are derivatives of barium metaplumbate BaPbO₃. When doped with some bismuth in place of lead, the material BaPb_0.95Bi_0.05O₃ exhibits superconductivity at 13 K. At the time of this discovery, oxides did not show such properties. The surprise associated with this work was eclipsed by the advent of the cuprate superconductors.

Binary lead oxides

Lead tetroxide ("red lead"), a valence-mixed oxide with formula Pb₃O₄ (red), may be thought of as lead(II) orthoplumbate(IV), [Pb²⁺]₂[PbO4−4]. Lead sesquioxide, Pb₂O₃, is also known (reddish yellow), and has the structure of lead(II) metaplumbate(IV), [Pb²⁺][PbO2−3].